package com.example.springbootspringclouddemo;
import java.util.HashMap;
import java.util.Map;
public class LRUCacheDemo {
class Node<K,V> {
K key;
V value;
Node<K,V> prev;
Node<K,V> next;
public Node() {
this.prev=this.next=null;
}
public Node(K key,V value) {
this.key=key;
this.value=value;
this.prev=this.next=null;
}
}
class DoubleLinkedList<K,V> {
Node<K,V> head;
Node<K,V> tail;
public DoubleLinkedList() {
head = new Node<K, V>();
tail = new Node<K, V>();
head.next = tail;
tail.prev = head;
}
public void addHead(Node<K,V> node) {
node.next = head.next;
node.prev = head;
head.next.prev = node;
head.next = node;
}
public void removeNode(Node<K,V> node) {
node.next.prev = node.prev;
node.prev.next = node.next;
node.prev = null;
node.next = null;
}
public Node getLast() {
return tail.prev;
}
}
private int cacheSize;
Map<Integer,Node<Integer,Integer>> map;
DoubleLinkedList<Integer,Integer> doubleLinkedList;
public LRUCacheDemo(int cacheSize) {
this.cacheSize = cacheSize;
map = new HashMap<>();
doubleLinkedList = new DoubleLinkedList<Integer, Integer>();
}
public int get(int key) {
if (!map.containsKey(key)) {
return -1;
}
Node<Integer,Integer> node = map.get(key);
doubleLinkedList.removeNode(node);
doubleLinkedList.addHead(node);
return node.value;
}
public void put(int key,int value) {
if (map.containsKey(key)) {
Node<Integer,Integer> node = map.get(key);
node.value = value;
map.put(key,node);
doubleLinkedList.removeNode(node);
doubleLinkedList.addHead(node);
} else {
if (map.size() == cacheSize) {
Node<Integer,Integer> lastNode = doubleLinkedList.getLast();
map.remove(lastNode.key);
doubleLinkedList.removeNode(lastNode);
}
Node<Integer,Integer> newNode = new Node<>(key,value);
map.put(key,newNode);
doubleLinkedList.addHead(newNode);
}
}
public static void main(String[] args) {
LRUCacheDemo lruCacheDemo = new LRUCacheDemo(3);
lruCacheDemo.put(1,1);
lruCacheDemo.put(2,2);
lruCacheDemo.put(3,3);
System.out.println(lruCacheDemo.map.keySet());
lruCacheDemo.put(4,1);
System.out.println(lruCacheDemo.map.keySet());
lruCacheDemo.put(3,1);
System.out.println(lruCacheDemo.map.keySet());
lruCacheDemo.put(3,1);
System.out.println(lruCacheDemo.map.keySet());
lruCacheDemo.put(3,1);
System.out.println(lruCacheDemo.map.keySet());
lruCacheDemo.put(5,1);
System.out.println(lruCacheDemo.map.keySet());
}
}